Field of the Invention
The technical field of the invention relates to methods for measuring morpho-geometric parameters of a spectacle wearing individual. These parameters may, for example, include the pupillary distance PD, the height H separating the pupil from the lower edge of a glass, the pantoscopic angle ΘP, which is the angle of inclination of the glasses relative to the facial plane of the individual, the distance DVO between the eye and the glass V, and the center of rotation CRO of the eye. Knowledge of these parameters is essential if a pair of spectacles, and in particular a pair of progressive glasses, is to be correctly personalized.
Description of Related Art
Methods allowing a certain number of these morpho-geometric parameters to be measured already exist. A first category of these methods employs a large vertical measuring column, with a video camera adjusted to eye height, the spectacle wearing individual looking into a mirror. This type of apparatus is very bulky and therefore a large room is required to carry out the measurements, furthermore it is relatively inflexible operationally insofar as it may neither be moved easily in order to refine the measurements, nor disassociated into a number of elements in order to be adapted to a given situation or environment.
A second category of methods, which is for example described in patent US 2010/195045, involves a measuring tablet able to measure the heights and the pantoscopic angle, the angle of inclination of the tablet being used to correct the values of said heights and said pantoscopic angle. However, such methods do not return very precise height and pantoscopic angle values if the angle of inclination of the tablet is too high. Specifically, they are completely satisfactory only for very small angles of inclination of the tablet, greatly limiting the number of possible measuring configurations and therefore impacting the operational flexibility of this tablet. Methods employing a tablet with limited functionality have their ergonomics compromised.
Objects and Summary
The methods for measuring morpho-geometric parameters according to the invention employ an apparatus that is both operationally flexible and able, easily and rapidly, to take precise and reliable measurements of said parameters, while preventing the spectacle wearing individual from having to tolerate even the slightest discomfort. Specifically, throughout the method the individual adopts a comfortable posture, with a natural inclination of the head, without ever having to tolerate a measurement protocol requiring them to adopt repetitive and uncomfortable postures, or ever having to wear additional equipment necessary for taking measurements. The methods according to the invention are also designed to return the results of the measurements automatically and rapidly. They are therefore reliable, precise and rapid while remaining operationally flexible and ergonomic.
In the rest of the description, the terms “spectacles”, “pair of spectacles” or “frame” are understood to be equivalent.
One subject of the invention is a method for measuring at least one morpho-geometric parameter of a spectacle wearing individual, said method employing a stand-alone information-processing device comprising a screen, a target, a compact image-acquisition system provided with a means for determining its inclination and connected to said screen, and a processor allowing the image-acquisition system to be controlled and the images obtained to be processed. The principal feature of a measuring method according to the invention is that it comprises the following steps:                adjusting the inclination of the image-acquisition system so that it remains in a permissible angular range, said image-acquisition system being equipped with a device for compensating for its inclination, so as to obtain an image of the eyes of the individual, which image is always centered on the screen whatever the inclination of said system in the permissible angular range;        adjusting the height of the image-acquisition system so that the individual can view the target along a substantially horizontal vision axis;                    the individual observing the target in a comfortable position that requires no particular effort to adopt, the spectacles occupying a natural position on the face of the individual;                        acquiring at least one image of the eyes and of the frame in said observation position by means of the image-acquisition system;        processing said at least one image using the processor in order to determine each morpho-geometric parameter of the individual from the position of their pupils and the inclination of their spectacles; and        returning the results of the measurements.        
The principle behind a measuring method according to the invention consists in adjusting, as precisely as possible, the image-acquisition system, in order to make it possible for the spectacle wearing individual to place themselves comfortably and unconstrainedly in front of said image-acquisition system while said method is carried out. The image-acquisition system may comprise at least one camera or at least one video camera. The inclination of the axis of the image-acquisition system must be known with precision especially in order to correct parallax errors due to this inclination, and which could corrupt the measurements. The term “compact” attributed to the image-acquisition system means that said system is small in size, and that it may be easily handled in order to be placed on an everyday piece of furniture such as a table or desk, and/or to be inclined. The target is preferably borne by the image-acquisition system in order to simplify the equipment employed to carry out the measuring method according to the invention. Advantageously, the target is positioned at substantially the same height as the image-acquisition system, and must form an identifiable point that the individual may easily focus on with their spectacles, even without their habitual correction. It may take the form of a specific added pattern, having a shape, a color and/or a visible relief, but it may also be a constituent element of the image-acquisition system having a very specific function, such as a flash or the lens of a video camera and/or of a camera. The images taken by the acquisition system must mainly show the frame of the spectacles, positioned relative to the eyes of the individual. Specifically, all the information required to carry out information-processing of the images in order to obtain the sought-after parameters must appear dearly in said images, via the spatial position of said frame relative to the eyes of the individual. It is therefore essential that both the frame and the eyes of the individual appear clearly and precisely in the images. The morpho-geometric parameters are then easily deduced from said photos using everyday trigonometric relationships. The inclination of the image-acquisition system must be limited to a permissible angular range, if not the measurements will be biased by introducing an excessively large angular offset. Said image-acquisition system is assumed to be preprogrammed to operate in this permissible angular range, and outside of this range it is assumed that it can no longer acquire images. Thus, the person handling the image-acquisition system no longer needs to worry about its inclination. The frame may optionally be provided with a referencing means taking the form of a clip equipped with markers, in order to allow its precise orientation in space in an image and its inclination to be viewed. The main function of the screen is to allow images taken by the acquisition system to be viewed. The screen may also be used to return the results of the measurements of the sought-after morpho-geometric parameters. The method may be carried out either by the spectacle wearing individual themselves, or by an operator, possibly an optician. It is assumed that the screen possesses a visible central zone, in which the acquired image must be displayed, in order for the latter to be entirely exploitable. This active compensation of the inclination, which allows the eyes and the frame to be positioned, in real time, in the central zone of the screen provided for this purpose, makes large-amplitude inclination of the image-acquisition system, in the permissible angular range, possible because this compensation removes the risk that all or part of the image will leave the display screen. The compensation device is based on an image-processing software package that selects, in the image obtained by the acquisition system, in which image the face of the individual appears off-center, the zone around the eyes and the frame of the individual, and moves said zone to the center of said screen.
Preferably, the compensation consists in moving each image obtained by the acquisition system to the center of the screen, the direction and the amplitude of movement of each of said images being dependent on the direction of inclination of the acquisition system and on the value of the angle of inclination.
Preferably, the permissible angular range is plus or minus 10° about a vertical reference position. The reference position of the image-acquisition system is assumed to be a vertical position for which the central sight axis of said system is horizontal. Advantageously, the permissible inclination range is comprised between 2° and 8°, in one direction or the other.
Advantageously, the spectacles of the individual are equipped with a clip provided with at least one marker, and the inclination of the frame is evaluated using a single video camera. Specifically, the clip, which is provided with markers, allows the inclination of the frame on the face of the individual to be viewed with precision. In this case, only one video camera is required to determine this inclination, from the dimensional characteristics of said clip in the image captured by the video camera. It is assumed that said video camera forms an integral part of the image-acquisition system employed in the method according to the invention.
According to another preferred embodiment of a method according to the invention, the inclination of the frame is evaluated by means of two video cameras used in stereoscopic mode. For this configuration, two separate video cameras, placed in two different locations and each filming the frame, allow the inclination of said frame to be determined without recourse to a marking clip. For this configuration it is assumed that the two video cameras belong to the image-acquisition system employed in the method.
Advantageously, the means for determining the inclination of the image-acquisition system is an inclinometer housed in said system.
Preferably, the information-processing device is provided with an alarm that is triggered when the angle of inclination of the acquisition system departs from the permissible angular range. This alarm may be an audible or visual alarm, and may take any form, the most important thing being for the person using the image-acquisition system to be made aware of the fact that they cannot take images when this alarm is activated. It is preferable for this alarm to appear on the image-acquisition system, so that the person handling this system receives the warning directly and instantaneously. The alarm may for example consist of a constant or flashing colored light that appears on the screen. It could also take the form of an identifiable sound, which would be triggered once the system was inclined too far.
Preferably, the morpho-geometric parameters measured by means of a method according to the invention are to be chosen from the group consisting of the height between the pupil and the lower rim of the glass, the pantoscopic angle, the face form angle of the spectacles and the pupillary distance.
According to one preferred embodiment of a method according to the invention, said method is implemented by the spectacle wearing individual, who adjusts the position of the image-acquisition system with reference to the pictures displayed by the screen, and utilizes the processor to trigger the image capture and the processing of said images. Specifically, the measuring method according to the invention may be carried out by a spectacle wearing individual possessing a suitable information-processing device. This device could be a home computer equipped with a webcam, an inclinometer and a suitable image-processing software package.
According to another preferred embodiment of a method according to the invention, said method is implemented by an optician placed facing the individual, and who utilizes the image-acquisition system to adjust its position in space, the optician guiding the individual and using the processor to trigger the image capture and the processing of said images. In this embodiment, the constituent elements of the information-processing device are arranged differently than when implemented by a single person. Specifically, the optician must have access to the screen and to the image-acquisition system, in order to adjust the position of said system depending on the images appearing on said screen. As for the spectacle wearing individual, they must position themselves facing said image-acquisition system following the instructions of the optician, who guides them through all the steps of the method.
Advantageously, the results of the measurements are displayed on the screen. Specifically, it is important, to improve the ergonomics of the method according to the invention, for the results of the measurements to appear rapidly and directly on a visual medium that can be read easily and unambiguously by the spectacle wearing individual and/or the optician. Other means may also be used, such as a printed document printed by a printer connected to the processor.
Preferably, the method comprises a step of adjusting the distance between the image-acquisition system and the face of the individual, so as to ensure that this distance lies in an acceptable range. Although the measuring method according to the invention has a certain operational flexibility, it remains limited in terms of the distance separating the individual and the image-acquisition system. Specifically, the face of the individual, essentially represented by their eyes, and the frame of the spectacles that they are wearing must occupy a certain zone of the screen, and with sufficient resolution to allow certain details of said face and said frame to be pinpointed. However, beyond a certain distance the face will be badly positioned on the screen or will be too small, the resolution then not being high enough to identify the sought-after details. It is therefore important to control this distance.
The invention also relates to an information-processing device for implementing a method according to the invention. The main feature of an information-processing device according to the invention is that it comprises a processor, a target, at least one video camera equipped with an inclinometer, and a display screen allowing the pictures taken by each video camera and the results of the measurements to be viewed. This measuring device is equivalent to a measuring kit, in which the various parts are connected to one another in order to interact and deliver the desired measurements, without necessarily being restricted to a particular arrangement. Specifically, this type of device has a certain flexibility in terms of its setup, in contrast to a fixed column, and may therefore be easily installed in any type of environment, whether it is on a table or a desk or quite simply on the ground. The processor allows pictures to be taken at the desired times, and also makes it possible for the images obtained to be processed. Preferably, the target is borne by the image-acquisition system.
Preferably, the position of the video camera and the position of the screen may be adjusted independently of each other.
Advantageously, the measuring device consists of a tablet combining the screen, a secondary video camera, the inclinometer and the processor, and of said at least one video camera. This version of the device is one of the most compact, and it may therefore be installed in a small space. Combining various constituent parts of the device in a small tablet further increases the operational flexibility of the measuring device, because an individual or an operator may carry out the method in its entirety using one and the same object, and make the necessary adjustments without having to reposition themselves, or move the parts relative to one another. A tablet is assumed to be an object the small size of which is compatible with easy manual handling by an individual or an operator. This type of object may, in particular, be easily moved manually in a room, in order to be installed in a precise location and to be oriented in the desired direction. This tablet may possess a touch screen, or more conventionally be operated by means of a mouse. It may also comprise at least two video cameras in order to carry out stereoscopic parameter measurements, such as a measurement of pantoscopic angle for example. The video camera may be fastened directly to this tablet, or to a stand allowing said tablet to be supported.
Methods for measuring morpho-geometric parameters of an individual according to the invention have the advantage of being particularly ergonomic and user-friendly for a spectacle wearing individual, insofar as the latter does not need to wear additional equipment and does not have to adopt a series of repetitive and constraining postures. Everything is organized so that the spectacle wearer passes through the various steps of the method while keeping a natural and comfortable posture. In addition, methods according to the invention have the advantage of instantaneously returning, to the individual or the optician, the results of the measurements, either by way of a screen or by way of any other means able to clearly and instantaneously deliver this information. Lastly, the measuring device employed in a method according to the invention has the advantage of being small in size and therefore easily adjusted and/or installed in a small room, on a table or on a desk.